gap-factint binary package in Ubuntu Lunar amd64

 GAP is a system for computational discrete algebra with particular
 emphasis on computational group theory, but which has already proved
 useful also in other areas.
 .
 This package brings to GAP routines for factoring integers, in particular:
  - Pollard's p-1
  - Williams' p+1
  - Elliptic Curves Method (ECM)
  - Continued Fraction Algorithm (CFRAC)
  - Multiple Polynomial Quadratic Sieve (MPQS)
 .
 It also provides access to Richard P. Brent's tables of factors of integers
 of the form b^k +/- 1.

Source package